#include <iostream>
#include <cmath>
using namespace std;

int main() {
    double x1,y1,x2,y2,x3,y3;
    double p, s;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

    double a,b,c;
    a = sqrt(pow((x1-x2), 2) + pow((y1-y2), 2));
    b = sqrt(pow((x2-x3), 2) + pow((y2-y3), 2));
    c = sqrt(pow((x1-x3), 2) + pow((y1-y3), 2));
    p = (a+b+c) / 2;
    s = sqrt(p*(p-a)*(p-b)*(p-c));
    printf("%.2f", s);
    return 0;
}